Molecular mapping of a gene conferring resistance to Phytophthora capsici Leonian race 2 in pepper line PI201234 (Capsicum annuum L.)

Phytophthora blight is one of the most destructive diseases affecting pepper production. Exploring resistance genes and transferring them into cultivated lines are critical for pepper (Capsicum annuum L.) breeding and disease control. To understand the genetics of resistance to Phytophthora capsici race 2 in pepper line PI201234 and identify molecular markers that are tightly linked to the gene, an F2 population containing 794 individuals was developed by crossing a susceptible line, Shanghaiyuan, to PI201234. Genetic analysis indicated that the resistance in PI201234 to P. capsici race 2 was controlled by a dominant gene, tentatively named CaPhyto. Using 12 markers, comprising 10 SSR markers, one CAPS marker, and one dCAPS marker, the gene was mapped to a 3.3-cM interval on chromosome 5. Based on genome sequence annotations in pepper line Zunla-1 and transcriptional expression analysis, two genes, Capana05g000764 and Capana05g000769, were identified as candidate genes. One SSR marker, ZL6726, most closely linked to CaPhyto at a distance of 1.5 cM, was validated to be a reliable marker for selecting phenotypes of resistance to P. capsici race 2. The results obtained in the present study will facilitate cloning and marker-assisted selection for resistance genes in pepper.